Scalable spectrum CDMA communication systems and methods with dynamic orthogonal code allocation

ABSTRACT

At least a portion of a total spectrum bandwidth of a wireless system may be allocated to each of a plurality of users by assigning at least one unique spreading code to each of the plurality of users. At least two of the plurality of users may have different spectrum capabilities and may transmit simultaneously. Each of the assigned spreading codes may have a different code length. The number and/or the code length of the spreading codes assigned to each user may be indicative of a portion of the total spectrum bandwidth allocated to each user.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Example embodiments of the present invention relate to wirelesscommunications systems. For example, at least some example embodimentsof the present invention relate to methods and apparatuses for providinga scalable spectrum, spectrum bandwidth and/or throughput to users in awireless communication system.

2. Description of the Conventional Art

Code division multiple access (CDMA) techniques (e.g., IS-95, cdma2000,Wideband CDMA (WCDMA), etc.) employ code channels for transmittinginformation to multiple users simultaneously. Each code channel isdistinguished by a unique spreading code (e.g., Gold codes, Walsh codes,OVSF codes, etc.). WCDMA is a 3^(rd) Generation wireless technology thatutilizes a higher spectrum bandwidth than, for example, IS-95 CDMA. Withthe increased spectrum bandwidth, WCDMA provides higher data rates orthroughput to wireless users. Universal Mobile TelecommunicationsSystems (UMTS) may utilize WCDMA as a suitable transport mechanism.

FIG. 1 illustrates a portion of a CDMA wireless system referred to as aCDMA cell site or cell. As shown, the CDMA cell site includes a basetransceiver station (BTS) 110 and a radio interface part. The BTS 110may communicate with a radio network controller (RNC) (not shown) as iswell-known in the art. The combination of one or more BTSs and an RNC isreferred to as a radio access network (RAN).

The BTS 110 may include multiple radio transceivers for communicatingwith the RNC and a plurality of users UE₁, UE₂, UE₃, . . . UE_(n) viathe radio interface part. As used herein, the term “user,” may besynonymous with mobile station, mobile user, user equipment (UE),subscriber, wireless terminal and/or remote station and may describe aremote user of wireless resources in a wireless communication network.For example, user equipment may be a mobile phone, wireless equippedcomputer, wireless equipped personal digital assistant (PDA), etc.

Referring still to FIG. 1, BTS 110 and the plurality of users UE₁, UE₂,UE₃, . . . , UE_(n) may communicate in the forward link (e.g., from BTSto user) or the reverse link (e.g., from user to BTS) simultaneously viacode channels. The code channels in the forward link, for example, maybe differentiated from each other by a unique spreading code (e.g., aGold code, Walsh code, OVSF code, etc.). A unique spreading code may beassigned to each user by the BTS 110. The code channels in the reverselink may also be differentiated in a similar manner.

Combining data signals with a unique spreading code spreads eachindividual data signal over a much wider spectrum (e.g., 5 MHz forWCDMA) than the spectrum (e.g., 15 kHz for speech data signal) occupiedby the data signals prior to spreading. After spreading, the BTS 110combines all spread data signals, and transmits the resultant signal toeach user served by the BTS 110. Each user is informed of its assignedspreading code via a separate signaling channel as is well-known in theart. Spreading the data signal over a wider spectrum allows for reducedtransmission power while still obtaining a suitable data rate and/orthroughput.

In one example, upon receiving the resultant signal transmitted from theBTS 110, user UE₁ identifies the data signal intended for user UE₁ usingthe same unique spreading code used to spread the data signal at the BTS110. Other data signals spread using other spreading codes are seen byuser UE₁ as noise. The length of a spreading code assigned to each useris dependent upon the information data rate assigned to the user and/orthe spectrum capability of each user. For example, the wider thespectrum capability of the user, the longer the assigned spreading codewill be for the same information data rate. This is a result of thelarger spectrum over which the data signal may be spread.

Referring still to the above example, at user UE₁ the de-spread datasignal is sent to a filter that allows the energy associated with thereceived data signal to pass, while reducing the interference. Thesignal-to-noise ratio (SNR) is determined by the ratio of the datasignal power to the sum of all of the other signal powers. The SNR isenhanced by the processing gain, that is, the ratio of the spectrum overwhich the data signal has been spread to the baseband data rate.

To provide higher throughput and/or information data rates required bywireless applications, for example, on the forward link, the BTS 110 andusers UE₁, UE₂, . . . , UE_(n) may operate in a larger spectrum (e.g.,10 MHz or 20 MHz). Conventionally, these higher spectrum bandwidthrequirements are satisfied by allowing users to access multiple carriers(e.g., multiple 5 MHz carriers in WCDMA) simultaneously whilemaintaining each individual carrier structure. This is referred to an Nxsystem. An Nx system allows backward compatibility with existingsystems. However, utilizing an Nx system may increase the cost ofradio-frequency (RF) design for users due to added RF path componentsand/or may introduce cross-carrier interference due to imperfect filterresponse in single carrier frequency designs.

SUMMARY OF THE INVENTION

Example embodiments of the present invention provide methods,apparatuses and a wireless communication system with a scalablebandwidth, employing dynamic spreading code (e.g., unique orthogonalcode) assignment for users with different spectrum capability (e.g.,dynamic CDMA). Example embodiments of the present invention are backwardcompatible with the narrower spectrum systems, eliminate cross-carrierinterference and/or provide improved or optimal performance.

At least one example embodiment of the present invention provides amethod for allocating at least a portion of a total spectrum bandwidthfor a multi-carrier wireless system to a plurality of users transmittingsimultaneously. At least a portion of the total spectrum bandwidth maybe allocated to each of a plurality of users by assigning at least oneunique spreading code to each of the plurality of users. At least two ofa plurality of users may have different spectrum capabilities and/oreach of the assigned spreading codes may have the same code length. Thenumber of spreading codes assigned to each user may be indicative of aportion of the total spectrum bandwidth allocated to each user.

At least one other example embodiment of the present invention providesa method for allocating at least a portion of a total spectrum bandwidthfor a multi-carrier wireless system to a plurality of users transmittingsimultaneously. At least a portion of the total spectrum bandwidth maybe allocated to each of a plurality of users by assigning at least oneunique spreading code to each of the plurality of users. In this exampleembodiment, at least two of the plurality of users may have differentspectrum capabilities, and at least two of the assigned spreading codesmay have different code lengths. The length of a spreading code assignedto a user may be indicative of the total spectrum bandwidth allocated tothe user.

In at least some example embodiments of the present invention, each ofthe plurality of users may be associated with a spectrum bandwidth classbased on a spectrum capability associated with each user. The codelength may be based on the spectrum bandwidth class of the user having ahighest spectrum capability. The spectrum bandwidth class associatedwith each user may be indicative of a spectrum over which each userreceives transmitted signals.

In at least some example embodiments of the present invention, thenumber of spreading codes assigned to each user may depend on at least atarget throughput associated with each user. The portion of the totalspectrum bandwidth assigned to each user may increase as the number ofspreading codes assigned to each user increases. At least two of theplurality of users may be assigned a different number of spreading codesbased on a target throughput associated with each of the plurality ofusers.

In at least some example embodiments of the present invention, themethod may further include determining a number of spreading codes toassign to each of the plurality of users based on at least a targetthroughput associated with each user, and allocating a portion of thetotal spectrum bandwidth by assigning spreading codes based on thedetermining step. The assigned spreading codes may be selected from acode tree or Hadamard matrix based on the determining step.

In at least some example embodiments of the present invention, themethod may further include comparing target throughputs associated witheach user, and assigning at least two spreading codes to at least a userhaving a largest associated target throughput. A code pattern of eachcode assigned to each of the plurality of users may depend on thespectrum bandwidth capability of each user.

In at least some example embodiments of the present invention, each ofthe plurality of users may be associated with a spectrum bandwidthclass, and the spectrum bandwidth class may be based on a spectrumcapability associated with each user. The length of each spreading codemay be based on the spectrum bandwidth class of the user to which thespreading code is assigned. The spectrum bandwidth class associated witheach user may be indicative of a spectrum over which each user receivestransmitted signals. The length of the spreading code assigned to eachof the plurality of users may be inversely proportional to the portionof the total spectrum bandwidth assigned to each of the plurality ofusers.

In at least some example embodiments of the present invention, at leasttwo of the plurality of users may be assigned spreading codes havingdifferent code lengths based on at least a target throughput associatedwith each of the plurality of users.

In at least some example embodiments of the present invention, themethod may further include determining at least one of a length of aspreading code and a number of spreading codes to assign to each of theplurality of users based on a target throughput associated with eachuser. The total spectrum bandwidth may be allocated by assigningspreading codes based on the determining step.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawings,wherein like elements are represented by like reference numerals, whichare given by way of illustration only and thus are not limiting of thepresent invention and wherein:

FIG. 1 illustrates a portion of a conventional CDMA wireless system;

FIG. 2 illustrates an apparatus according to an example embodiment ofthe present invention;

FIG. 3 illustrates a simple example code tree; and

FIG. 4 illustrates an example correlation between assigned codes andspectrum for a wireless system.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Although the following description relates to a communication network orsystem based on CDMA technologies such as WCDMA/UMTS, and will bedescribed in this example context with respect to FIG. 1, it should benoted that the example embodiments shown and described herein are meantto be illustrative only and not limiting in any way. For example,methods and/or apparatuses according to example embodiments of thepresent invention may be utilized in conjunction with any wirelesstechnology, such as, IS95, cdma2000, various technology variationsand/or related technologies. Various modifications will be apparent tothose skilled in the art for application to communication systems ornetworks based on technologies other than the above, which may be invarious stages of development and intended for future replacement of, oruse with, the above networks or systems.

Example embodiments of the present invention will be described hereinwith respect to transmissions in the forward link (e.g., from BTS touser); however, it will be understood that example embodiments of thepresent invention may be equally applicable to transmissions in thereverse link (e.g., from user to BTS).

As described above, the term user may be synonymous with mobile station,mobile user, user equipment (UE), subscriber, wireless terminal and/orremote station and may describe a remote user of wireless resources in awireless communication network.

Example embodiments of the present invention relate to methods andapparatuses for providing scalable spectrum, spectrum bandwidth and/orthroughput to a plurality of users dynamically. At least one exampleembodiment of the present invention provides a method and apparatus forassigning one or more spreading codes to users according to the spectrumbandwidth class of the BTS, the spectrum bandwidth class of the user,spectrum requirements of the user, a target throughput and/or a targetinformation data rate associated with each user. Spectrum bandwidthclass refers to the spectrum capability of transceivers at, for example,BTS 110 or users UE₁, UE₂, . . . , UE_(n). Spectrum capability refers tothe maximum spectrum bandwidth over which a BTS and/or a user mayreceive a transmitted signal, for example, in the forward link. That is,for example, the maximum spectrum over which the data signal may bespread. Spectrum requirements, target throughput and/or data rate may bedependent on, for example, the data rate requested by respective users,type of traffic being transmitted to each user (e.g., voice, data,video, etc.), etc.

As will be discussed, for the same information data rate, users withlarger spectrum capabilities may be assigned longer codes as compared tousers with smaller spectrum capabilities. According to exampleembodiments of the present invention, the assigned spreading codes, evenfor different users with different spreading capabilities, may have thesame lengths. Alternatively, the lengths may be different. That is, forexample, BTSs may transmit data signals spanning different spectrumbandwidths based on assigned spreading codes. The spectrum of thewireless system may become scalable based on the spreading code assignedto each user scheduled to receive a transmission in the forward link.

Example embodiments of the present invention may be implemented in anycommunication system having a system spectrum B satisfying the equationB=2^(N) B₀, where B₀ is the “single-carrier” bandwidth and 2^(N) is thenumber of carriers supported by the communication system. For example,in a WCDMA system, the single carrier bandwidth B₀ may be 5 MHz, and thesystem may support 8 carriers. Therefore, the WCDMA system may have atotal system spectrum bandwidth of 8B₀ or 40 MHz because B₀=5 MHz andN=3. As discussed herein, “system spectrum bandwidth,” refers to the RFtransceiver capability of the wireless system, or in other words, thespectrum over which the BTS and user transceivers may be capable ofspreading data signals to be transmitted (e.g., in the forward link).

As discussed above, FIG. 1 illustrates a cell site of a CDMA wirelesssystem. Example embodiments of the present invention will be describedwith regard to the cell site shown in FIG. 1 and with regard to a CDMAsystem; however, example embodiments of the present invention, may beequally applicable to any wireless communication system (e.g., CDMA,cdma2000, IS-95, etc.).

Referring to FIG. 1, BTS 110 may serve a plurality of users UE₁, UE₂,UE₃, . . . , UE_(n), and each of BTS 110 and users UE₁, UE₂, UE₃, . . ., and UE_(n) may be grouped into spectrum bandwidth classes based on thenumber of carriers supported by each. That is, for example, BTS 110 maysupport 2^(N) carriers, and thus, may belong to a spectrum bandwidthclass N. Similarly, user UE₁ may support 2^(j) carriers, and thus, maybelong to a spectrum bandwidth class j. In other words, spectrumbandwidth classes, as discussed herein, may be identified by the numberof supported carriers (e.g., N for BTS 110 or j for user UE₁), and eachBTS and/or user UE₁, UE₂, . . . UE_(n) may belong to a differentspectrum bandwidth class.

In one example, older legacy users may be capable of transmitting and/orreceiving narrowband signals (e.g., data signals spread over a spectrum2^(j)B₀, where j=0). These narrowband users may be associated with aspectrum bandwidth class j=0 because each user may support only a singlecarrier. Newer, enhanced users may be capable of transmitting and/orreceiving both narrowband and wideband signals (e.g., data signalsspread over a spectrum 2^(j)B₀, where j=1, 2 or 3, etc.). For example,these newer users may be associated with a spectrum bandwidth class j=3because each user in this spectrum bandwidth class may support 8carriers. The BTS 110 may also be associated with a spectrum bandwidthclass N=3 because the BTS 110 may support a maximum of 8 carriers.

FIG. 2 is a block diagram illustrating an example embodiment of thepresent invention. The example embodiment shown in FIG. 2 may beimplemented using a processor such as a digital signal processor (DSP)or application specific integrated circuit (ASIC). Alternatively, theexample embodiment of FIG. 2 may be implemented at least in part in theform of a computer software program stored in a memory or externalstorage device. Such a program may be executed, for example, by aprocessor. The processor used to implement and/or execute the exampleembodiment shown in FIG. 2 may be one of a plurality of processorsincluded at a conventional BTS such as BTS 110. The apparatus of FIG. 2may be included along with well-known circuitry at BTSs such as the BTS110. As shown, the apparatus of FIG. 2 may include a scheduler 202, acode assignment module (CAM) 204 and a baseband signal generation module206. An example embodiment of the present invention will be describedwith regard to the CDMA cell site of FIG. 1.

The scheduler 202 may schedule a plurality of users for simultaneoustransmission (e.g., from BTS to user) at a given time. The maximumnumber of users that may be scheduled for simultaneous transmission maybe dependent on the spectrum bandwidth class of the BTS 110. Forexample, if the BTS 110 belongs to a spectrum bandwidth class N=3 (e.g.,the BTS 110 supports 8 carriers), the scheduler 202 may schedule amaximum of 2³ or 8 users for simultaneous transmission at any giventime. The BTS 110 may schedule users for transmission according to anywell-known or specially designed scheduling algorithm. For example, thescheduler 202 may schedule users based on link quality, priority oftraffic intended for each user, quality of service (QOS) requirements,user priority level, etc.

Within the maximum of 2^(N) users scheduled for simultaneoustransmission, the scheduler 202 may schedule a maximum of J usersassociated with a respective spectrum bandwidth class, where J=2^(j).For example, if the scheduler 202 schedules 8 users for transmission,only maximum of 2 users may belong to spectrum bandwidth class j=1because J=2¹=2. Similarly, only a maximum of 4 users belonging tospectrum bandwidth class j=2 may be scheduled because J=2²=4, and only amaximum of 8 users belonging to spectrum bandwidth class j=3 may bescheduled because J=2³=8. The total number of scheduled users, however,may not be greater than 2^(N).

After scheduling users for simultaneous transmission at a given time,the scheduler 202 may identify the scheduled users, spectrum bandwidthclass of each scheduled user, spectrum requirements and/or targetthroughput associated with each scheduled user to the CAM 204. Theoperations, processes and/or methods performed by the CAM 204 will bediscussed in more detail below.

The CAM 204 may assign one or more spreading codes to each scheduleduser based on, for example, the spectrum bandwidth class of eachscheduled user, spectrum requirements and/or target throughputassociated with each scheduled user. As stated above, the BTS 110 andusers UE₁, UE₂, UE₃, . . . , UE_(n) may transmit data signals overwireless code channels differentiated by unique spreading codes. Inexample embodiments of the present invention, the unique spreading codesassigned to each scheduled user may result in the scaling of thewireless channel over which each user may receive transmitted datasignals.

Each of the assigned spreading codes may be a unique orthogonal binarycode (e.g., a Gold code, a Walsh code, an OVSF code, etc.). Exampleembodiments of the present invention will be discussed with regard toWalsh codes; however, any suitable spreading code may be utilized inconjunction with example embodiments of the present invention.

In one example, the CAM 204 may assign spreading codes all of which are2^(N) chips long. In another example, the CAM 204 may assign spreadingcodes which vary in length from 2⁰ chips to 2^(N) chips, inclusive. TheCAM 204 may assign spreading codes selected from, for example, aWalsh-Hadamard matrix or code tree.

FIG. 3 illustrates a simple, example code tree. As shown, the Walshcodes are uniquely described as W_(SF,m,) where SF is the spreadingfactor of the code and m is the code number 0≦m≦SF−1. Namely, each codetree defines Walsh codes of length SF, corresponding to a spreadingfactor of SF as shown in FIG. 3, and each Walsh code of spreading factorSF may have a unique code pattern identified by the code number m.

Referring back to FIGS. 1 and 2, the CAM 204 may select the codes fromthe code tree based on, for example, spectrum bandwidth class of eachscheduled user, spectrum requirements and/or target throughputassociated with each scheduled user. Methods for assigning spreadingcodes to users, according to example embodiments of the presentinvention, will be discussed in more detail below by way of example.However, it will be understood that the example embodiments of thepresent invention may be implemented on much larger scales (e.g., usinglarger and/or more complex code trees), and in any suitable wirelesscommunication system. The following examples will be discussed withregard to FIG. 1, assuming that the scheduler 202 at BTS 110 hasscheduled users UE₁, UE₂ and UE₃ for simultaneous transmission at agiven time.

In one example embodiment, the CAM 204 may assign spreading codes eachof which have a same length of 2^(N) chips. In this example, each usermay be assigned a spreading code having the same length regardless ofwhich spectrum bandwidth class each user belongs. In this example,however, the code pattern assigned to each user may depend on thespectrum bandwidth class to which each user belongs.

As discussed above, N refers to the number of carriers supported by thewireless system (e.g., in a wireless system in which B=2^(N)B₀, 2^(N)=8,N=3 and thus, the wireless system effectively has 3 single carriers ofbandwidth B₀) The CAM 204 may assign one or more spreading codes to eachscheduled user such that, for each scheduled user, the assignedspreading code bears the signature:

$C = {\underset{\underset{2^{N - j}}{︸}}{c_{0}c_{0}\ldots\mspace{11mu} c_{0}}\underset{\underset{2^{N - j}}{︸}}{c_{1}c_{1}\ldots\mspace{11mu} c_{1}}\ldots\mspace{11mu}\underset{\underset{2^{N - j}}{︸}}{c_{k}c_{k}\ldots\mspace{11mu} c_{k}}}$

where c₀c₁ . . . c_(k) is a spreading code of length k=2^(j).

The CAM 204 may assign at least one or more spreading codes to eachscheduled user to increase throughput and/or information data rate basedon the target throughput associated with each scheduled user. That is,for example, the CAM 204 may assign multiple spreading codes to one ormore scheduled users if the CAM 204 determines that increased throughputand/or information data rate is necessary. The CAM 204 may determinethat increased throughput and/or information data rate is necessarybased on the target throughput associated with each scheduled user. Forexample, if the target throughput is higher for user UE₁ compared touser UE₂, the CAM 204 may assign the user UE₁ multiple spreading codes,while assigning user UE₂ a single spreading code, or a lesser number ofspreading codes as compared to those assigned to user UE₁.

The following examples of the manner in which codes may be assigned bythe CAM 204 to scheduled users UE₁, UE₂ and UE₃ win be discussed withregard to the above code signature C, the cell-site of FIG. 1 and theexample code tree of FIG. 3.

For example, if B=8B₀ (i.e., 2^(N)=8 and N=3) for the cell-site of FIG.1, and user UE₁ supports a spectrum bandwidth of 2B₀ (i.e., 2^(j)=2 andj=1), the CAM 204 may select a maximum of two spreading codes from atotal of four available spreading codes having the signatureC=c₀c₀c₀c₀c₁c₁c₁c₁ to be assigned to UE₁. In this example, onlyspreading codes having the signature C=c₀c₀c₀c₀c₁c₁c₁c₁ are availablefor assigning to UE₁ because j=1, N=3 and 2^(N-j)=4. Referring back tothe simple code tree of FIG. 3, the four available spreading codes maybe ‘11111111’, ‘11110000’, or the corresponding complementary codesthereof ‘00000000’ and ‘00001111’.

Similarly, if user UE₂ supports a spectrum bandwidth of 4B₀ (i.e.,2^(j)=4 and j=2), the CAM 204 may select a maximum of four spreadingcodes from a total of eight available spreading codes having thesignature C=c₀c₀c₁c₁c₂c₂c₃c₃ to be assigned to user UE₂. In thisexample, only spreading codes having the signature C=c₀c₀c₁c₁c₂c₂c₃c₃are available for assigning to UE₂ because j=2, N=3 and 2^(N-j)=2.Referring again to the code tree of FIG. 3, the eight availablespreading codes may include ‘11111111’, ‘11110000’, ‘11001100’,‘11000011’, or the corresponding complementary codes thereof ‘00000000’,‘00001111’, ‘00110011’ and ‘00111100’.

In another similar example, if user UE₃ supports a spectrum bandwidth of8B₀ (i.e., 2^(j)=8 and j=3), the CAM 204 may select a maximum of eightspreading codes from a total of sixteen available spreading codes havingthe signature C=c₀c₁c₂c₃c₄c₅c₆c₇ to assign to user UE₃. In this example,only spreading codes having the signature C=c₀c₁c₂c₃c₄c₅c₆c₇ areavailable for assigning to UE₃ because j=3, N=3 and 2^(N-j)=1. Referringagain to the simple code tree of FIG. 3, the available spreading codesfor UE₃ may include ‘11111111’, ‘11110000’, ‘11001100’, ‘11000011’,‘10101010’, ‘10100101’, ‘10011001’, ‘10010110’, or the correspondingcomplementary codes thereof, ‘00000000’, ‘00001111’, ‘00110011’,‘00111100’, ‘01010101’, ‘01011010’, ‘01100110’, ‘01101001’.

In the above examples, the same spreading code may not be assigned tomore than one of users UE₁, UE₂ and UE₃, and each scheduled user may beassigned one or more spreading codes having an appropriate codesignature. Table 1 illustrates an example code assignment by the CAM204, the code signaled to the users (via a separate signaling channel asis well-known in the art) and the resultant spectrum bandwidth overwhich data signals are spread by the BTS 110.

TABLE 1 Assigned Code Signaled Resultant Scheduled User Code to UserSpectrum user UE₁ of 11110000 10  B₀ 2B₀: user UE₂ of 11001100 1010 2B₀4B₀: 11000011 1001 user UE₃ of 10101010 10101010 4B₀ 8B₀: 1010010110100101 10011001 10011001 10010110 10010110

As shown from the above example, the greater number of codes assigned toeach scheduled user, the larger the spectrum over which the userreceives transmitted signals. As is well-known in the art, the greaterthe spectrum, the higher the resultant information data rate and/orthroughput. Thus, according to example embodiments of the presentinvention, the greater the number of spreading codes assigned to eachscheduled user, the higher throughput and/or information data rate forthe user.

In the above example, each assigned spreading code results in abandwidth B₀ being allocated to the scheduled user. In this example, theaggregate bandwidth allocated to each scheduled user is equal to thenumber of assigned codes multiplied by the single carrier bandwidth B₀.As shown above, for example, user UE₃ may be assigned four spreadingcodes, and thus, user UE₃ may be allocated a spectrum bandwidth of 4B₀.This may result in a higher throughput and/or information data ratethan, for example, user UE₁ and user UE₂ who have been assigned onespreading code and two spreading codes, respectively.

As discussed above, the CAM 204 may assign spreading codes to usersscheduled for simultaneous transmission at any given time based on thespectrum bandwidth class of each user, spectrum requirements and/or atarget throughput associated with each scheduled user. Referring to theabove example, the example code assignment shown in Table 1 may be usedin the event that the scheduled user UE₃ requires a higher data rate orthroughput as compared to the scheduled users UE₁ and UE₂.

In another example, the CAM 204 may assign spreading codes varying inlength from 2⁰ chips to 2^(N) chips, inclusive based on the spectrumbandwidth class of each user, spectrum requirements and/or targetthroughput associated with each user. As in the previous example, thefollowing example will be discussed with regard to the code signature C,the cell-site of FIG. 1 and the code tree of FIG. 3. In addition, thisexample will be described with regard to the same users UE₁, UE₂ and UE₃scheduled for simultaneous transmission at a given time.

In this example, spreading codes may be assigned by the CAM 204 to usersUE₁, UE₂ and UE₃ in the same manner as described above, except that theassigned spreading codes may differ in length. The length of assignedspreading code may imply (or carry) a different spectrum, throughputand/or information data rate to be assigned to each user. That is, forexample, the spreading codes may still be assigned such that theassigned spreading code bears the signature:

$C = {\underset{\underset{2^{N - j}}{︸}}{c_{0}c_{0}\ldots\mspace{11mu} c_{0}}\underset{\underset{2^{N - j}}{︸}}{c_{1}c_{1}\ldots\mspace{11mu} c_{1}}\ldots\mspace{11mu}\underset{\underset{2^{N - j}}{︸}}{c_{k}c_{k}\ldots\mspace{11mu} c_{k}}}$

where c₀c₁ . . . c_(k) is a spreading code of length k=2^(m), and m=0,1, . . . , j; however, the spreading codes may be less than 2^(N) chipslong.

In this example embodiment, the shorter the assigned code, the greaterthe assigned spectrum, throughput and/or information data rate. Thecorrelation between the assigned spectrum and the spreading codeassigned to each user may be expressed by Equation 1 shown below.

$\begin{matrix}{{AssignedSpectrum} = {\frac{2^{N}}{k_{UEi}}B_{0}}} & {{Equation}\mspace{20mu} 1}\end{matrix}$

In Equation 1, N is the spectrum bandwidth class of the BTS or wirelesssystem, and k_(UEi) is the length of the spreading code assigned to userUE_(i,) for i=1, 2, 3, . . . n.

In addition, assignment of any spreading code blocks or restricts theuse of any subordinate spreading code (e.g., longer spreading codebeneath the assigned code) in the code tree (of FIG. 3, for example).This restriction is well-known in the art, and thus, a detaileddiscussion of this will be omitted for the sake of brevity.

As in the previous example, assume the spectrum bandwidth B for thecell-site of FIG. 1 is 8B₀ and N=3. If user UE₃, belonging to spectrumbandwidth class j=3, is assigned a code 8 chips in length (e.g.,‘10101010’), the effective spectrum bandwidth assigned to user UE₃ is B₀even though the data signal may be spread over the entire spectrum 8B₀.

On the other hand if user UE₃ is assigned a code 2 chips in length(e.g., ‘10’), the effective spectrum bandwidth assigned to user UE₃ is4B₀, and all other codes under the 2 chip spreading code in the codetree may not be assigned to any other user scheduled for the samesimultaneous transmission. For example, with regard to the code tree ofFIG. 3, if user UE₃ is assigned the code ‘10’, then none of spreadingcodes in the code tree under node ‘10’ may be assigned to otherscheduled users, for example, users UE₁ or UE₂, scheduled for the samesimultaneous transmission. In this example embodiment, the CAM 204 mayassign a single spreading code to each user, or multiple spreading codesto each user.

Referring back to FIG. 2, after the CAM 204 assigns spreading codes toeach scheduled user (in either of the above mentioned example manners),the baseband signal generation module 206 may combine (e.g., add inbinary space) the spread signals from scheduled users UE₁, UE₂ and UE₃to generate a baseband signal (e.g., a forward link (FL) basebandsignal) to be transmitted. The combining performed by the basebandsignal generation module 206 may be done in any well-known manner, andas such, a detailed discussion has been omitted for the sake of brevity.

Concurrently, the spreading code assigned to each user UE₁, UE₂ and UE₃may be conveyed to each user via a separate signaling channel. Thisconveyance may also be performed before the baseband signal is actuallytransmitted or delivered to the users, and may be done via any suitablesignaling channel as is well-known in the art. Because these signalingchannels are well-known, a detailed discussion has been omitted for thesake of brevity. The combined signal may be transmitted to the usersUE₁, UE₂ and UE₃ by a transmitter (not shown) in any well-known manner.

FIG. 4 shows an example correlation between assigned codes and spectrumbandwidth over which a data signal is spread for a wireless system withB=4B₀. FIG. 4 will be discussed with regard to UE₂ for example purposes.As discussed above, user UE₂ may belong to spectrum bandwidth class j=2.That is, for example, in the case of FIG. 4, the user UE₂ supports themaximum spectrum bandwidth B=4B₀.

Referring to FIG. 4, if the code ‘1111’ is assigned to user UE₂, thedata signal is spread over single carrier spectrum bandwidth B₀.Alternatively, assigning code 1100 to user UE₂ may result in the samedata signal spanning a spectrum bandwidth of 2B₀. Furthermore, assigningcode ‘1010’ to user UE₂ may result in the same signal spanning theentire spectrum bandwidth 4B₀. In each of the examples shown in FIG. 4;however, the user UE₂ achieves the same throughput or information datarate while the spectrum power may be decreased as the spectrum bandwidthincreases.

Example embodiments of the present invention provide a more costeffective RF chain design by removing multiple single-carrier filters.Moreover, example embodiments of the present invention may improveforward link RF capacity, reduce the inter-carrier guard band and/ormore efficiently utilize spectrum resources because the cross-carrierinterference may be reduced for older, legacy users and/or eliminatedfor newer, enhanced users.

Although the foregoing description focuses on methods for transmittingwideband signals via a radio communication system adapted fortransmitting narrow-band signals, persons of ordinary skill in the artwill readily appreciate that the techniques of the present invention arein no way limited to radio communication systems, systems transmittingsignals with only two distinct bandwidths, or to systems adapted fortransmitting narrowband signals. On the contrary, any communicationsystem which might benefit from shared access to a plurality offrequencies by two or more transceivers transmitting and/or receivingsignals at two or more bandwidths may employ the techniques shownherein. Such systems might include systems employing methods fortransmitting narrow-band signals via a radio communication systemadapted for transmitting wideband signals. Further, wired systems suchas computer networks could employ the techniques provided herein withoutdeparting from the scope of the invention.

Example embodiments of the present invention have been described withregard to spectrum bandwidth. However, it will be understood that in atleast some instances, spectrum bandwidth may be synonymous withbandwidth, spectrum, data rate, etc.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the invention, and all such modifications are intended tobe included within the scope of the invention.

1. A method for allocating at least a portion of a total spectrumbandwidth for a multi-carrier wireless system to a plurality of userstransmitting simultaneously, the method comprising: allocating at leasta portion of the total spectrum bandwidth to each of a plurality ofusers by assigning at least one unique spreading code to each of theplurality of users, at least two of a plurality of users havingdifferent spectrum capabilities and transmitting simultaneously, each ofthe assigned spreading codes having a same code length, and a number ofspreading codes assigned to each user being indicative of a portion ofthe total spectrum bandwidth allocated to each user, wherein each of theplurality of users is associated with a spectrum bandwidth class basedon a spectrum capability associated with each user, the spectrumcapability of a respective user being a number of supported carriersassociated with a maximum supported bandwidth of the respective user. 2.The method of claim 1, wherein the code length is based on the spectrumbandwidth class of the user having a highest spectrum capability.
 3. Themethod of claim 2, wherein the spectrum bandwidth class associated witheach user is indicative of a spectrum over which each user receivestransmitted signals.
 4. The method of claim 1, wherein the number ofspreading codes assigned to each user depends on at least a targetthroughput associated with each user.
 5. The method of claim 1, whereinas the number of spreading codes assigned to each user increases, theportion of the total spectrum bandwidth assigned to each user increases.6. The method of claim 1, wherein at least two of the plurality of usersare assigned a different number of spreading codes based on a targetthroughput associated with each of the plurality of users.
 7. The methodof claim 1, further comprising: determining a number of spreading codesto assign to each of the plurality of users based on at least a targetthroughput associated with each user; and wherein the total spectrumbandwidth is allocated by assigning spreading codes based on thedetermining step.
 8. The method of claim 7, wherein the assignedspreading codes are selected from a code tree or Hadamard matrix basedon the determining step.
 9. The method of claim 1, further comprising:comparing target throughputs associated with each user; and wherein atleast two spreading codes are assigned to at least a user having alargest associated target throughput.
 10. The method of claim 1, whereina code pattern of each code assigned to each of the plurality of usersdepends on the spectrum bandwidth capability of each user.
 11. Themethod of claim 1, wherein a spectrum bandwidth class of each of theplurality of users is indicative of decoding capabilities of each user.12. The method of claim 1, wherein a code pattern of the at least oneunique spreading code assigned to each of the plurality of users dependson a spectrum bandwidth class of each user.
 13. A method for allocatingat least a portion of a total spectrum bandwidth for a multi-carrierwireless system to a plurality of users transmitting simultaneously, themethod comprising: allocating at least a portion of the total spectrumbandwidth to each of a plurality of users by assigning at least oneunique spreading code to each of the plurality of users, at least two ofthe plurality of users having different spectrum capabilities andtransmitting simultaneously, at least two of the assigned spreadingcodes having different code lengths, and the code length of a spreadingcode assigned to a user being indicative of the total spectrum bandwidthallocated to the user, wherein each of the plurality of users isassociated with a spectrum bandwidth class based on a spectrumcapability associated with each user, the spectrum capability of arespective user being a number of supported carriers associated with amaximum supported bandwidth of the respective user.
 14. The method ofclaim 13, wherein the length of each spreading code is based on thespectrum bandwidth class of the user to which the spreading code isassigned.
 15. The method of claim 14, wherein the spectrum bandwidthclass associated with each user is indicative of a spectrum over whicheach user receives transmitted signals.
 16. The method of claim 13,wherein the code length is inversely proportional to the portion of thetotal spectrum bandwidth assigned to each of the plurality of users. 17.The method of claim 13, wherein at least two of the plurality of usersare assigned spreading codes having different code lengths based on atleast a target throughput associated with each of the plurality ofusers.
 18. The method of claim 13, further comprising: determining atleast one of a code length of a spreading code and a number of spreadingcodes to assign to each of the plurality of users based on a targetthroughput associated with each user; wherein the total spectrumbandwidth is allocated by assigning spreading codes based on thedetermining step.
 19. The method of claim 18, wherein the assignedspreading codes are selected from a code tree or Hadamard matrix basedon the determining step.